What is Dark Matter?
Dark matter is the hypothetical form of matter that accounts for 85% of the mass in the universe. It is believed that most of this matter is in the form of dark particles, and does not interact with ordinary matter. The discovery of this form of matter has fueled the current rethinking of the structure of the universe. Some of the latest observations from WMAP and Planck, as well as laboratory searches, are promising for the detection of this type of particle.
CMB measurements confirm expansion of the universe is speeding up
A map of the CMB has been released, offering a new measurement of how fast the universe is expanding. Moreover, the map also offers a new way to measure the age of the universe.
The CMB is a faint, uniform electromagnetic radiation that has been measured by several different instruments. Its intensity is proportional to the frequency of its light. However, it is not associated with any particular star or object.
Some of the best measurements of the CMB have come from the Planck and WMAP space telescopes. These satellites imaged CMB at higher resolution and a greater temperature sensitivity. This has revealed subtle large-scale features of the CMB.
One measurement, called the Hubble constant, has been debated among physicists. Its value is 69 kilometers per second per megaparsec. That number is based on the assumption that the universe was formed in the big bang.
According to some estimates, the expansion rate of the universe has accelerated. When the universe was half its current size, its temperature was a little bit warmer, at 5.46 K. In about 10 billion years, it will cool to 1.36 K.
Other experiments confirm the presence of dark matter. Another measurement, called the polarization of the CMBR, will also reveal tensor perturbations caused by density perturbations. Moreover, future measurements will be able to directly observe cosmological gravitational waves.
As with many scientific discoveries, there are many competing explanations for the CMB. Whether it is a cosmic microwave background or something else entirely, it has many interesting characteristics. For example, it is the only relic of the past when the universe was still in its early stages.
Observations by WMAP and Planck
Dark matter is a mysterious substance that is invisible to the human eye but which influences the structure of the universe. It is believed to make up at least five-sixths of the matter in the universe. In the absence of dark matter, galaxies would fly apart. Instead, they are gravitationally bound and orbit each other at predicted orbital velocities of general relativity.
Dark matter is a form of non-baryonic matter that interacts with ordinary matter in a subtle fashion. The particles that comprise dark matter are not able to interact with electromagnetic interactions. This leads to an increase in radiation pressure. These effects have led to speculation that dark matter is composed of sub-atomic particles.
Several astronomical observations have been used to verify the existence of dark matter. One type of observation is the distribution of mass in galaxy clusters. Some argue that this distribution shows the presence of self-interaction.
Another type of observation is the speed of rotating galaxies. Using this data, Vera Rubin proved the existence of dark matter. Her results, which were independently confirmed in 1978, were based on the velocity curves of edge-on spiral galaxies.
Another type of evidence is the existence of ripples in the cosmic microwave background (CMB). Ripples are echoes of gas vibrations in the early universe.
Observations have shown that the density of dark matter has increased as a fraction of total matter. These observations also suggest that dark matter has a hard spectrum. The hard spectrum is characterized by more electrons in higher frequencies.
Several detectors have been built to see possible signals from WIMP particles. While many have been unsuccessful, one has seen a stronger signal.
Laboratory searches have the potential to detect halo dark matter particles
Many experiments around the world have been investigating dark matter particles. They use a variety of techniques. Some aim to detect particles, while others look for indirect evidence.
Dark matter particles are believed to have masses less than ten times the mass of the proton. They interact with normal matter only weakly. These interactions can be detected using signatures in cosmic rays.
Scientists have been searching for dark matter particles for over thirty years. However, they are still unsure of how dark matter particles interact with normal matter. There are three types of particle candidates: hot, cold, and warm. The next generation of experiments will use systems with unprecedented sensitivity.
Researchers hope to identify dark matter particles in the laboratory. This would provide a window to the unknown. Detecting the particles could help cosmologists and astrophysicists understand their existence and composition.
The Large Hadron Collider (LHC) may be able to detect dark matter particles. It has been used to crash two high-energy protons into one another. Other experiments, such as the SuperCDMS collaboration, are looking for dark matter particles in the laboratory.
The detection of dark matter is important for astrophysics and particle physics. As a result, the DOE Office of Science High Energy Physics program is funding research to find the origin of these particles.
In addition, the WMAP experiment has found small irregularities in the cosmic microwave background. These traces of energy are believed to be caused by dark matter particles passing through the Earth.
There are several different types of dark matter particles, and researchers have been trying to create them in the laboratory. Currently, the best candidates are neutrinos and supersymmetric particles.
Gravitational lensing can measure cluster masses without relying on observations of dynamics
Using the lensing effect as a natural telescope, astronomers can observe the distribution of mass in a cluster of galaxies. These observations are important in a variety of astrophysical applications. They can also be used to map the properties of black holes.
In the first method, a mathematical model is used to determine the properties of the lens and source. A second method uses X-ray or velocity distributions to determine the mass. The third method involves using the virial theorem to calculate the mass.
Observations have shown that gravitational lenses appear in the outer regions of galaxy clusters. This is because gravity is magnifying the background galaxies. For example, the Hubble Space Telescope (HST) recently observed a giant luminous arc in CL1358+62.
In the past decade, gravitational lensing has appeared in popular science magazines and has captured the public’s imagination. As a result, the number of people working in the field is increasing.
It has also been discovered that the effects of lensing can be measured by measuring the time delay of light curves. This can help determine the mass of a black hole. However, the process is not precise.
Another possible application of gravitational lensing is to estimate the cosmological distance scale. The scale of the universe can be mapped, with a large enough distance difference, and a proper mapping can be used to understand the motions of sources near a black hole.
Other branches of astronomy have also found use for gravitational lensing. Various astrophysical problems are studied through lensing, including star-formation and cosmological parameters.
Many of the phenomena studied through gravitational lensing are too complicated to be predicted with precision. However, extrapolating these concepts should allow future applications of gravitational lensing.
Effect of dark matter on galaxies
Dark matter is a substance that interacts with visible matter and causes gravitational attraction. Its effects on galaxies are relatively small. But it makes up a large proportion of the universe, as astronomers have found.
Scientists estimate that dark matter is a large fraction of the universe. There are two major categories of dark matter. The nonbaryonic type is thought to make up 27 percent of the total.
This dark matter can be divided into hot and cold categories. Cold dark matter is particles that are slow moving. They are referred to as weakly interacting massive particles.
Observing the density and speed of the cosmic microwave background can reveal the presence of dark matter. It is a relic from the Big Bang. In the early days of the universe, photons of light were 2.7 million Kelvins.
Dark matter’s effect on galaxies is not completely understood. Researchers have observed the effects of gravitational lensing, which distorts the brightness of the background. This has the effect of magnifying light from distant objects. As such, it can be used to measure the mass of clusters.
A team led by Pavel E. Mancera Pina recently reported the discovery of six ultra-diffuse gas-rich galaxies. These elliptical galaxies show signs of having been formed from nonbaryonic dark matter.
Researchers have also studied the effects of galaxy clusters on light. Although this technique is not conclusive, it provides an indication of the effect of dark matter on galaxies.
Astronomers have also discovered several galaxies that do not have dark matter. The NGC 1052-DF2 is one of these galaxies. This object does not have a central dark matter “cusp” that would have been expected from the standard model of cosmology.
If you like what you read, check out our other science articles here.